Microconnector for FPC connection and method of producing the same

ABSTRACT

A micro connector comprising an insulator holding a lever, a printed circuit board which has a plurality of micro contacting terminals at a back surface thereof and an FPC cable which has a plurality of micro contacting pieces in an end thereof, wherein said insulator guides said FPC cable.

TECHNICAL FIELD

The present invention relates to a micro connector used for a flexibleprinted circuit cable (called a FPC micro connector).

BACKGROUND ART

The recent electronic apparatus and equipment have been being developedunder the concept of the needs and requirement of “thinner” and“lighter” and the high packing density of electronic componentsinstalled in the apparatus and equipment has been attempted. One of themajor technologies to realize this high packing density is to use aflexible printed circuit cable (abbreviated as an FPC cable,hereinafter) which has characteristics of flexibility in theinstallation in various apparatuses and equipment.

Micro connecters to be used for the FPC cables have been enabling cableassembly in curved wiring and three dimensional installation withflexibility such as bending, twisting as well as satisfying the needsand requirements for “thinner” and “lighter” apparatuses and equipment.According to such feature, FPC cables have been adopted in thecommercial products such as portable phones that require lightness andthinness as the devices. An example of the FPC micro connectors has beendisclosed in the reference 1.

Reference 1:

Japanese laid open patent, 2000-048885

The FIGS. 7A to 7C show cross sectional views of the conventionalconnector 10. FIG. 7A shows the physical status before an FPC cable 30is inserted to the connector 10. FIG. 7B shows the status after an FPCcable 30 is inserted to the connector 10 and FIG. 7C shows the statusafter an FPC cable 30 is clamped by a lever 22 set in the connector 10.

As shown in FIG. 7A, the housing 25 has an opening in the upper portion,side walls 26 in the both sides (a single side in the figure is drawn)and many slits (not shown in the figures) like as gaps between combteeth. The housing, which is combined in a single unit with the slits towhich many contacts 14 like as comb teeth are inserted therein, isattached to the printed circuit board 29.

The contacting piece 17 and the fixing piece 18 of the contact 14 clampsthe salient 27 from the upper side and the lower side and the terminalportion 20 of the elastic support 15 of the contact 14 is substantiallyformed into a column shape. The lever 22 can rotate without interferencearound the terminal portion 20 which is formed into such substantiallycolumn shape at the terminal portion 20 of the elastic support 14. Onthe upper surface of the contacting piece 17, a contactor portion 19which electrically contacts with the contacting terminal 31 formed theback surface of the FPC cable 30.

When the lever 22 is rotated in the arrow direction as shown in the FIG.7B after the FPC cable 30 is set in the predetermined position on thehousing 25, the FPC cable 30 is fixed in the physical status that thecontacting terminal 31 (see FIG. 6) contacts with the contactor portion19.

As shown in FIG. 8, the contacting terminals 31 are arranged in a pitchof 0.3 mm on back surface of the FPC cable 30 so that the contactingterminals 31 contact with the contactor portion 19 of the contactingpiece 17 of the contact 14. For the manufacturing of the FPC microconnector, high precision press-forming and etching pattern forming havebeen used and the minimum forming pitch P can be as small as 0.1 mm. Thefinal form of the contacting terminal 31 is rounded at the edges due tothe etching process.

However, the quantity of the wires set in the FPC cable tends toincrease in accordance with the requirement for the high-speed operationand the high integration of the devices in the recent booming anddiffusion of portable telephones with built-in cameras, mobilecommunication services and internet communication. As the results, thereis a problem that conventional FPC micro connectors cannot beaccommodated in the limited inner room of the devices such as portablephones.

In order to satisfy the requirements for the application for portablephones, such that highly electrical insulation not to make shortageamong wires even for narrowing of the adjacent terminals is maintainedand therefore high reliability of terminal contact and high performanceportable phones are satisfied, a large capacity FPC micro connector havebeen desired.

For this purpose, there is a strong demand for ultra-small FPCconnectors that support the electronic devices which are in progress tomultiple functionalities and high performances, a printed circuit boardwhich has plurality of fine connection terminals and a FPC cable thathas a high density contacting terminal.

DISCLOSURE OF THE INVENTION

The present invention is regarding a connector to connect FPC cables toprinted circuit boards preferably comprises an insulator holding a leverwherein the insulator guides the FPC cable, a printed circuit boardwhich has a plurality of micro contacting terminals at a back sidethereof and an FPC cable which has a plurality of micro contactingpieces in an end thereof.

“High density” implies the pitch P of the contacting terminals arearranged in less than 0.1 mm and a “micro connector” contactingterminals and connecting devices which are aligned in high density.

According to this connector, it is possible to connect the FPC cabledirect to the printed circuit board and increase the connectionterminals in large extent so that the width of the FPC cable can beshrunk down. The conventional parts which are used for the conventionaltechnologies are not necessary and the height of the whole connector canbe shrunk down to a half size of the conventional connector. Therefore,it is possible to provide high density FPC micro connectors.

The contacting terminals of the FPC cable of the connector regarding thepresent invention are preferred to be directly connected to thecontacting terminals formed on the printed circuit board.

In other words, by placing the contacting terminals corresponding to thecontacting terminals of the FPC cable on the upper surface of theprinted circuit board, the main body of the micro connector comprisestwo parts as a clumping lever and an insulator so that the half heightof the connector body can be realized, the process steps for formingprocesses and assembly processes are reduced in large extent ultra-smallFPC micro connector can be provided, as well as shortening theelectronic circuitry.

For the connector regarding the present invention, the cross sectionalshapes of the plurality of the ultra-small contacting terminals formedon the FPC cables is formed in an arch cross sectional shape at thecontacting surface.

Since the contacting surface is formed in a formed in arch crosssectional shape, the actual contact portions can be confined at twoedges formed in both side edges of the contacting terminal piece. Whenthe contacting terminal is pressed against the other contacting piece,the side edges of the contacting terminals are elastically deformed andcut oxide covering film on the other contacting terminal into the metalsurface of the contacting terminal. Therefore the contact is surelyperformed and the reliability can be twice as much as the conventionalcontact.

The present invention provides manufacturing method to make plurality offine contacting terminals on the FPC cable in order to electricallyconnect the FPC to the printed circuit board. The manufacturing methodfeatures to include the first step for the UV lithograph using thickphoto resin (or called as “photo resist”) as a called photo engravingprocess and the second step for micro plating process.

According to the present invention which combines the first step tocarry out UV lithography the second step to carry out micro plating, itis possible to form ultra small pitches which are not manufactured bythe conventional processes. Therefore, the present invention supportsthe increase of the quantity of the contacting terminals of the FPCcables, which is required by the needs of multiple functionalities to berealized in the electronic devices. The application for radio frequencysignal transmission, where the signal lines (SG) and the grand lines(GND) are alternatively arranged, is easily realized by the presentinvention and high reliability can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective schematic to show the FPC micro connectorregarding the present invention.

FIG. 2 (a) is another perspective schematic to show the physical statuswherein the micro connector case is removed from the printed circuitboard.

FIG. 2 (b) is an expanded cut view of the FPC contacting with theprinted circuit board along the cut line B-B shown in FIG. 2 (a).

FIG. 2( c) is an expanded cut view of the FPC contacting with theprinted circuit board along the section c shown in FIG. 2( b) to showthe arched surface of the micro contacting pieces.

FIG. 3( a) is a cross sectional view of the physical status before theFPC cable is inserted in the FPC micro connector.

FIG. 3( b) is a cross sectional view of the physical status after theFPC cable is inserted in the FPC micro connector.

FIG. 3( c) is a cross sectional view of the physical status that the FPCcable 7 is inserted in the FPC micro connector regarding the presentinvention and the FPC cable is pressed by the lever.

FIG. 4( a) is the left hand side schematic of the FPC cable.

FIG. 4( b) is the plan view of the FPC cable.

FIG. 4( c) is the front view of the FPC cable.

FIG. 4( d) is the zoomed-in view of the portion D shown in FIG. 4( a).

FIG. 4( e) is a plan view of the FPC cable which has contactingterminals in both ends.

FIG. 4( f) is the front view of the FPC.

FIG. 5 is a perspective schematic that shows the contacting terminalsformed on the FPC cable.

FIG. 6 is an explanatory schematic that shows the contacting terminalson the FPC cables

FIG. 7( a) is a cross sectional schematic that shows the physical statusof the conventional connector before the FPC cable is inserted therein.

FIG. 7( b) is a cross sectional schematic that shows the physical statusof the conventional connector when the FPC cable is inserted therein.

FIG. 7( c) is a cross sectional schematic that shows the physical statusof the conventional connector when the FPC cable is clamped by the leverattached to the connector.

FIG. 8 is a zoomed-in view of the cross section cut in the line C-C.

MODE(S) FOR CARRYING OUT THE INVENTION

We will explain the embodiments of the present invention in referring tothe figures.

As shown in FIG. 1, the FPC micro connector 1 comprises an insulator 2,a lever 3 and a printed circuit board 5 which has micro contactingpieces in the back surface thereof and an FPC cable 7 which has a microcontacting terminal 8 at the end and on the back side thereof.

As shown in FIG. 2 (a) and FIG. 2 (b), the printed circuit board 5 onwhich electronics parts are soldered and assembled has micro contactingpieces 6 which make the connection pieces separately formed inmicro-forming processes. The surfaces of the micro contacting pieces 6have planner ones. However, the micro contacting terminals 8 formed onthe back surface of the FPC cable 7 have an arch cross sectional shapewhich is in the cross sectional view and the contact of the microcontacting terminal 8 against the micro contacting piece 6 are at thetwo lines that are the end lines of the edges of the micro contactingterminal 8 at both ends in the widthwise. Since the two end lines of theedges of the micro contacting terminal 8 cut the oxide film or naturaloxidation layer covering the micro contacting piece 6 into thereof andfirmly contact therewith, the electronic contact between the microcontacting pieces 6 and the micro contacting terminals 8 has highreliability as more than twice against the conventional contact.

As a narrow pitch cabling due to large insulating capability, it ispossible to construct a radio frequency transmission circuitry byassigning the lines, which terminate at the micro contacting terminals8, alternatively for signal line (SG) and the ground lines (GND). Bythis construction, a high reliable and large line capacity FPC microconnector is obtained even for the pitch between the adjacent contactingterminals is small and therefore applicable to the portable phones forrealizing high performances. The pitch between the adjacent contactingterminals is 0.04 mm in the present embodiment.

Insulator

As shown in FIG. 3 (a), the insulator 2 guides the FPC cable 7 on theprinted circuit board 5 and keeps the FPC cable 7 to the predeterminedposition so that the micro contacting terminals 8 surely contact withthe micro contacting pieces 6 formed on the printed circuit board 5.

The insulator 2 is made of insulating material and constructs the mainbody of the FPC micro connector.

The physical dimensions of the insulator 2 for the present embodimentare 6 mm depth along the FPC cable 7, 10 mm width along the width of theFPC cable 7 and 0.9 mm height from the printed circuit board 5.

The axial line support 2 a of the insulator 2 mates the cylindricalrecess 3 a of the lever 3 and maintains the rotational motion of thelever 3 around the axial line support 2 a. The lever 3 has a part of cammechanism so that the gap between the outer surface of the lever 3 andthe facing surface of the printed circuit board 5 or the microcontacting pieces 6 varies in the rotational angle of the lever 3 andthe gap is large enough not to interrupt the insertion of the FPC cable7 when the lever 3 is pushed up to the release position as shown in FIG.3 (a).

The insulator has a flat base 2 b in the back side facing to the printedcircuit board 5. The flat base 2 b is fixed to the printed circuit board5, for example by an adhesive. The insulator 2 has two walls 2 c alongthe direction of the insertion of the FPC cable 7 and a groove 2 d ismade for each of the walls 2 c so that the FPC cable 7 is guided intothe insulator 2, which facilitates the positioning of the FPC cable 7against the height direction (thickness of the FPC cable 7) and widthdirection and therefore the correct positioning of the FPC cable 7 isfeasible in the insertion to the insulator.

Moreover, grooves 2 f are made between the top flat portion 2 e and thewalls 2 c, as shown in FIG. 1, so that the lever 3 can elastically pushthe FPC cable 7 against the printed circuit board 5 by pulling down thelever 3.

Lever 3

The lever 3 is such a small part that the arm length is only 5 mm. Thelever 3 is supported by the axial support formed at the end line of theinsulator 2 with rotational movable installation. After inserting theFPC cable 7 into the insulator 2 at the predetermined position, thelever 3 can push the micro contacting terminal 8 so that the microcontacting terminal 8 firmly contacts with the micro contacting piece 6formed on the printed circuit board 5 by means of rotating downwardlythe lever 3 of which rotation is done around the axial line support 2 aso that a part of FPC cable 7 which is exposing to the outside of theinsulator 2 connector is covered by the lever 3.

In the present embodiment, the rotation range of the lever 3 ispreferably 0 deg. to 110 deg. but can be 0 deg to 90 deg. against theplanar surface of the FPC cable 7.

The insulator 2 is fixed to the upper surface of the printed circuitboard 5 but does not entirely cover the micro contacting pieces 6 whichare to contact to the micro contacting terminals 8 formed on the FPCcable 7 so that some part of the micro contacting pieces 6 are exposingoutwardly.

FPC Cable

The FPC cable 7 is explained in the followings.

As shown in FIG. 4 (b), the FPC cable 7 has a shape of a thin ribbonwith 8 mm width. The FPC cable 7 is made of a thin film on which cablelines and circuitries are formed and the other thin film coveringthereon and therefore is durable against bending, over lapping, foldingand twisting.

As shown in FIG. 4 (d), on the back surface of the FPC cable 7,especially at the terminal thereof, the surface of the terminal portionof the FPC cable 7 is facing to the micro contacting piece 6 formed onthe printed circuit board 6 has 200 pieces of the micro contactingterminals 8 formed in the predetermined pitch (the pitch P is equal to0.04 mm (40 micrometers) for the present invention) along the directionof the width of the FPC cable.

Comparing with the conventional flexible flat cable (the pitch is 0.3 mm(300 micrometers)) that has the same width as that of the present FPCcable 7, the conventional flexible flat cable has 25 contactingterminals. However the present embodiment provides 200 pieces of themicro contacting terminals 8 and has been improved as eight timescircuit density. Therefore, the width of the connector can besufficiently narrowed so that further compactization and lightening ofthe devices is possible.

Micro Contacting Terminals

The micro contacting terminals 8 formed on the FPC cable 7 are facing tothe micro contacting pieces 6 and contacting therewith and electricalconnection is made between the FPC cable 7 and the printed circuit board5.

In the present embodiment, the FPC cable 7 that has substantially aribbon shape is used and the micro contacting terminals 8 have an archcross sectional shape.

The micro contacting terminals 8 which are formed in the same quantitiesof the micro contacting pieces 6 to make a one-to-one correspondingconnection are arranged on the back surface of the FPC cable 7 in thepredetermined pitch in the direction of the width direction of the FPCcable 7 when the electrical contact is made between the FPC cable 7 andthe printed circuit board 5.

As shown in FIG. 4 (b) and FIG. 5, the micro contacting terminals 8 havethe similar form as that of the micro contacting pieces 6, in otherwords, substantially a strip shape which has a sufficient length alongthe length of the FPC cable 7 to obtain satisfactorily electricalcontact with the micro contacting pieces 6. The width of the microcontacting terminals 8 is made narrower than that of the microcontacting pieces 6 so that the electrical contact of the microcontacting terminals 8 is surely made with the micro contacting pieces6.

As shown in FIG. 2 (b), FIG. 4 (d) and FIG. 5, the micro contactingterminals 8 formed on the surface of the back surface of the FPC cable 7has an arch shape and the salient edges 8 a of the micro contactingterminals 8 cut the oxide covering film on the micro contacting pieces 6terminal into the metal surface thereof.

In other words, the edges of the micro contacting terminals 8 in thewidth direction form salient edges 8 a. Therefore, the micro contactingpieces 6 formed on the printed circuit board 5 first contact to thesalient edges 8 a when the lever 3 is pushed downwardly so that thelever 3 rotates around the axial line support 2 a and the microcontacting terminals 8 formed on the FPC cable 7 is pressed against themicro contacting pieces 6 to make a contact thereto.

As shown in FIG. 6, when the pressing force F that presses the FPC cable7 down to the printed circuit board 5 is applied, the salient edges 8 aof the micro contacting terminals 8 plow the surface of the microcontacting pieces 6 in the direction of the width thereof in slightdeformation thereof.

Accordingly, even though oxide layer which baffles the electricalcontact is formed on the surface of the micro contacting pieces 6, it ispossible to surely obtain an electrical contact between the microcontacting terminals 8 formed on the FPC cable 7 and the microcontacting pieces 6 formed on the printed circuit board 5 because thesalient edges formed on the both sides of the micro contracting terminal6 cut a way the oxide layer covering and existing on the surface of themicro contacting piece 6 when the salient edges 8 a plow the surfaces ofthe micro contacting pieces 6.

In other words, the salient edges 8 a are elastically deformed andplowing the thin oxide layer formed on the micro contacting piece 6 bybeing pressed against the micro contacting piece 6 by means of the leveras shown in FIG. 3 and therefore the mechanism of the present inventioncan provide a sure electrical contact as an electrical connector system.

The micro contacting terminals 8 are preferably formed by an etchingprocess and an additional plating process. When the micro contactingterminals 8 are formed by an etching process, the edge of the microcontacting terminals 8 are rounded during such etching process (refer to“R” shown in FIG. 8 which is a conventional connector system). On theother hand when the micro contacting terminals 8 are processed with anadditional plating process, the both edges of the micro contactingterminals 8 grow into the salient edges 8 a having a corner angle of 85to 88 degrees. The contacting surface of the micro contacting terminals8 becomes to have an arch form.

Contacting Operation of FPC Micro Connector

The operation of the FPC micro connector 1 is explained in reference toFIG. 3.

As shown in FIG. 3 (a), we first rotate the lever 3 of the FPC microconnector 1 up to over the vertical angle (90 degrees) to a declinedangle as 110 degrees. The lowest surface of the lever 3 facing to theFPC cable 7 does not contact to the surface of the FPC cable 7 which isinserted into the insulator 2 since the opposite side of the lever 3 hasa radius changing in the rotational angle so that a part of an eccentriccam is formed.

As shown in FIG. 3 (b), we insert the FPC cable 7 from the right handside of FIG. 3 (b) as much as the tip of the FPC cable 7 touches thestopper 4 and then push down the lever 3 which rotates around the axialline support 2 a until the lever has been pulled down as shown in FIG. 3(c). The lowest surface of the lever 3 facing to the FPC cable 7 hascome down to have no gap with the FPC cable 7 since the opposite side ofthe lever 3 has a radius changing in the rotational angle.

In other words, as shown in FIG. 3 (c), it is possible to press themicro contacting terminals 8 on the FPC cable 7 against the microcontacting pieces 6 on the printed circuit 5 and make a sure electricalcontact between them by means of the elastic spring force generated bythe top flat portion 2 e of the insulator 2 when the lever 3 is pulleddown and set in horizontal position against the FPC cable 7.

In this setting of the lever 3, the oxide layer existing on the surfaceof the micro contacting piece 6 is cut a way by the salient edges 8 aplowing the surfaces of the micro contacting pieces 6, because the microcontacting terminals 8 have salient edges 8 a in both sides. As theresult, the micro contacting terminals 8 on the FPC cable 7 makes a sureelectrical contact and therefore it is possible to obtain the sufficientelectrical connection between them.

Manufacturing Method

The manufacturing method is explained in the followings.

The first step is to carry out UV photo engraving with thick photoresin. This process is to homogenously spread a photo resin on thesurface of the cupper foil plated on the cupper foiled board(abbreviated as a board for simplicity) which is to be fabricated as aprinted circuit board, bake the board for drying in 90 degree C.temperature and expose ultra-violet light through a photo mask contactedonto the photo resin which is on the board. After exposing with the UVlight, the resin is developed to form the pattern that is transferred tothe circuit pattern. The transfer is done by the developed resin patternthat blocks the etching. The un-etched portion becomes a pattern of thecircuit. This is substantially same micro fabrication process as thatused for the present invention.

In stead of coating resin on the board, a photo-sensitive dried film canbe used to make the etching pattern. The UV light is ultra-violet light.

The second step is a micro plating deposition process, which is one ofthe intrinsic properties of plating. As shown in FIG. 4 (d), this is atechnology to ultimately form an arch shape in the cross section of themicro contacting terminals 8.

The kind of the plating used in this invention is electrolysis plating.For the primary plating, nickel is plated on the copper foil that ispatterned for the circuit. The finishing may be gold plating. For thismanufacturing method, the pitch of the micro contacting terminals 8 canbe less than 0.1 millimeters or less as less as 40 micrometers andprovide a manufacturing method that overcomes the limitation of theconventional micro connectors.

Although there have been disclosed what are the patent embodiment of theinvention, it will be understood by person skilled in the art thatvariations and modifications may be made thereto without departing fromthe scope of the invention, which is indicated by the appended claims.

For example, we have discussed the FPC cable that has the microcontacting terminals at one end thereof in the previous discussion andit is possible that the FPC cable has the micro contacting terminals atboth ends thereof.

We have discussed the micro contacting terminals that have salient edgesbut it is preferred that the micro contacting pieces on the printcircuit boards alternatively have the salient edges.

As we have explained, the micro connector of the present invention canreduce the widths of the FPC cables since the FPC cables are connectedto the printed circuit boards by the micro connectors and the quantitiesof the connections can be largely increased. Alternatively using theconventional connector, the micro connector 1 can provide a half heightof the physical dimensions of the connector in comparison to theconventional ones.

According to the setting position of the micro connecting pieces 6 whichcorrespond to the micro connecting terminals 8 formed on the FPC cable,it is possible to provide a ultra small FPC micro connector that has theultimate height and the steps of fabrication processes and assemblyprocesses can be reduced to be a half height and be extremely shortened,other than to shorten the electrical circuit, since the FPC microconnector consists of the lever and the insulator.

Since the contacting surface of the micro contacting terminals 8 on theFPC cable 7 is curved and two edges of the micro contacting terminals 8make electrical contact and therefore the reliability can be doubled.

According to the present invention, the electrical metal terminals whichhave ultra-small pitches can be fabricated by combining the firstprocess that is the conventional UV photo engraving lithography and thesecond process that is an additional plating process so that theincreasing of quantity and the density of the terminals, which is asolution for the multi-function needs, can be provided.

INDUSTRIAL APPLICABIITY

It is possible to facilitate to realize a radio frequency circuit byalternatively placing signal lines and ground lines with highlyisolating each other and to apply to various applications.

By alternatively placing signal lines and ground lines with highlyisolating each other, high capacity FPC micro connectors, that supporthigh reliable usage, to be used for portable phones can be made even theline spaces are quite small.

1. A micro connector comprising an insulator holding a lever, a printedcircuit board which has a plurality of micro contacting pieces at a backsurface thereof and an FPC cable which has a plurality of microcontacting terminals in an end thereof, wherein said insulator guidessaid FPC cable to translate along said printed circuit board to permitthe FPC cable to be connected directly to the printed circuit boardthereby reducing the size of the micro connector; wherein at least oneof said plurality of micro contacting terminals and said microcontacting pieces has an arch cross sectional shape to define salientcontact edges that are adapted to elastically deform when said microcontacting terminals contact said micro contacting pieces.
 2. A microconnector according to claim 1, wherein said plurality of microcontacting terminals contact directly to said micro contacting pieces.3. A micro connector according to claim 2, wherein said plurality ofmicro contacting pieces has an arch cross sectional shape contactingsaid micro contacting terminals.
 4. A manufacturing method for a microconnector according to claim 1 including a first process for UVlithograph using thick photo resin and a second step for micro platingprocess.
 5. The micro connector according to claim 1, wherein said FPCcable lies directly against said printed circuit board.
 6. The microconnector according to claim 1, wherein said insulator comprisessidewall directly engaging said printed circuit board to leave saidplurality of micro contacting pieces on the printed circuit boardexposed, said FPC cable being inserted between said sidewalls anddirectly against said printed circuit board.